The invention relates to the field of integrated circuits and more particularly to the access of multiple functions or circuits of an integrated circuit from a limited number of input or output terminals of the integrated circuit.
For compact integrated circuits used in modern technology, especially for miniaturized devices such as those powered by batteries or used in laptop computers, it is often necessary to combine many functions into a small amount of (silicon) die area used in the integrated circuits and provide the functionality using the simplest interface with the least number of external connections or (terminal) pins.
In particular as new technology supplants older technology there may be a need to provide backward compatibility of integrated circuits so that new integrated circuit components can be used in place of old components, such as in the repair of older equipment, second sourcing of parts, or in the manufacture of different models of equipment where different functions may be activated through common terminals or pins on integrated circuits.
For instance, in the wireless data communication used in communications by some computers infrared standards have been adopted at certain points in time and then subsequently upgraded for improved communications. This has required improved integrated circuits and advanced programming to replace older hardware and software applications (which we will call legacy hardware and software ). The proposed standards put forward by the Infrared Data Association (IrDA) have become important for manufacturers to adopt throughout the PC industry due to wide acceptance of their infrared communication specifications. Accordingly it may be said that important defacto standards for infrared transceiver components have emerged in the marketplace from the point of view of their electrical signal interfaces.
Because of the presence of older (legacy) equipment and software in the marketplace and the use of the legacy equipment and manufacturers"" and customers familiarity and dependence on the older technology problems can arise when a newer generation product is being developed to adopt a more sophisticated digital programming interface (enhanced function) over the original product. Because of the use of the older equipment in the marketplace it has been found important to retain, in new products, the xe2x80x98look and feelxe2x80x99 (from a pinout and electrical interface point of view) of legacy devices. This means that the function of the pins that already had a standard industry mode of operation need to be shared in such that a manufacturer or user who is not interested in new function would see no change in the way they must interface to the device. The term xe2x80x98legacy modexe2x80x99 has been chosen to describe the original mode of operation that must be transparently supported from user""s point of view.
One aspect of the invention provides for a data processing system a method of discriminating between digital signals of a plurality of different rates by monitoring the pulse width and repetition rate of such signals comprising:
monitoring the digital signals for a preselected period of time;
determining whether only a single pulse or multiple pulses have been detected within the preselected time period; if only a single pulse or a portion thereof has been detected within the preselected time period generating a first type of control signal; if multiple pulses or portions of multiple pulses have been detected within the preselected time period generating a second type of control signal.
In another aspect, if only a single pulse has been detected within the preselected time period further discrimination may be made based on whether the pulse width is shorter or longer than the preselected time period.
If the pulse is less than a predetermined threshold timing period a third type of control signal may be generated, and if the pulse is greater than the predetermined timing period a fourth type of control signal may be generated.
The first type of control signal may be adapted to set the data processing system into a first mode of operation. The second type of control signal may be adapted to set the data processing system into a second mode of operation.
In another aspect, apparatus is provided for controlling a data processing system adapted to operate in a plurality of modes of operation for processing digital signals of a plurality of rates by selecting modes of operation of said system. This includes means for monitoring said digital signals for a preselected period of time; discrimination means for determining whether only a single pulse or multiple pulses have been detected within said preselected time period; control signal generating means for generating a first type of control signal if only a single pulse or a portion thereof has been detected within said preselected time period; control signal generating means for generating a second type of control signal if multiple pulses or portions of multiple pulses have been detected within said preselected time period.
The apparatus may include timing means which if only a single pulse has been detected within said preselected time period determines the width of said pulse.
The apparatus may include control signal generating means for generating a third type of control signal if said pulse is less than a predetermined threshold timing period and for generating a fourth type of control signal if said pulse is greater than said predetermined timing period.
The apparatus may be adapted wherein said first type of control signal is adapted to set said data processing system into a first mode of operation, and also wherein said second type of control signal is adapted to set said data processing system into a second mode of operation.
Another aspect of the invention herein is to provides a way to combine two (or more) different digital interface functions into a single circuit using the same set of input and output external pins. Normally, different circuit functions would require dedicated input/output pins. Advantages of the invention are such that when used in integrated circuits more functionality is available using the same number of pins, with the addition of this functionality being nearly transparent from a mode-to-mode perspective.